there should be an option in the bios to disable the floppy drive which should make it disappear from windows too.

Yeah... but why would my BIOS reset like that?

hard to say, done any overclocking? Some boards like to reset the bios after a crash if they think it was caused by overclocking (though you normally get some kind of extra message if this is the case).

If it keeps doing it I'd invest in a new cmos battery but if that doesn't fix it there could be some kind of problem with the board.

If you're asking why did it reset with the floppy on then... the board probably shipped with "optimised defaults" and when it reset it went back to an absolute default setting for safety. Since floppy drives are really old and back-in-the-day every PC was expected to have at least one there isn't anything built in to the system for actually detecting whether they're connected or not it's just assumed that they are unless the bios is told to report otherwise. (IIRC, its been a while since I thought about floppy drives)